Figure 1.
The top row of images show a stroke on DWI/ADC which has some enhancement on post contrast T1 imaging.
The bottom row shows the perfusion deficit on a TTP map, the permeability image when not corrected for arrival time, and the permeability image after arrival time correction. The green circles show corresponding areas of contrast leakage on the T1 post contrast and ATC permeability images. (DWI = diffusion weighted image, ADC = apparent diffusion coefficient, PWI = perfusion weighted image, TTP = time to peak, ATC = arrival time corrected).
Figure 2.
The two graphs show the ΔR2* for non-enhancing (control) and enhancing hypoperfused regions before and after arrival time correction (ATC).
In the first graph, due to even a small delay in time-to-peak, the control signal appears to approach baseline faster thus obscuring the phenomenon being measured. However, in the second graph, after the ATC has been applied to the control, it becomes evident that the enhancing region signal is approaching the baseline faster due to the T1 effect of contrast accumulation in the parenchyma.
Figure 3.
The receiver-operator characteristic (ROC) curves, which demonstrate the ability to correctly identify enhancing tissue, are plotted before and after arrival time correction (ATC).
Prior to correction the technique performs worse than random chance at some thresholds due to perfusion deficits.